18SOUND 15NMB420
18SOUND (Eighteen Sound) 15NMB420 — 15" / 15 inch · Woofer/Midrange (WM) · Subwoofer / Bass · Neodymium
3" voice coil · 4 Ω
Part no.: 42A-CHS-TT-18S-0057
Documents
18SOUND 15NMB420 — 15" · Woofer
450 W AES · 99 dB Sensitivity · Frequency range 40 Hz – 5000 Hz
Technical data
- Diameter: 15 "
- Voice coil: 3 "
- Power handling: 450 W AES
- Sensitivity: 99 dB
- Impedance: 8 Ω
- Magnet: Neo
- Weight: 3.9 kg
- Mounting depth: 169 mm
- Frequency range: 40 – 5000 Hz
Datasheet (PDF) · Manufacturer page
Series: NMB · Part no.: 42A-CHS-TT-18S-0057
18Sound 15NMB420: lightweight 15" neodymium bass-midrange driver with 99 dB
The 15NMB420 belongs to 18Sound's NMB series, the neodymium drivers for bass and midrange in one. Unlike a pure subwoofer it is tuned for speed and bandwidth, with a 3" voice coil, only 73 g of moving mass and a stated range of 40 Hz to 5000 Hz. The result is 99 dB sensitivity at 450 W AES – an efficiency that heavy subwoofer cones do not reach.
At 3.9 kg the driver is remarkably light and the mounting depth of 169 mm is shallow. The parameters Fs 42 Hz, Qts 0.29 and Vas 225 l describe a soft, large radiating area with a strong motor (BL 19 Tm); the inductance of 0.8 mH keeps the output from collapsing early at the top. Linear excursion of 6.5 mm is enough for bass in tops, not for subwoofer work.
Use and enclosure
The 15NMB420 is the classic bass-midrange driver for 2-way tops with a horn, or for the midrange section of large 3-way systems. With EBP 140 it belongs in a vented box; the guide value is about 97 l net, tuned to 54 Hz with an f3 around 62 Hz. That is a generous volume for a 15", caused by the high Vas. Used as a midrange in a 3-way system it needs its own sealed mid chamber, for which the guide value is around 46 l. Check both with the enclosure calculator at 42.audio.
At the top the 15NMB420 can be crossed to a compression driver in the region where a 1.4" or 2" unit takes over cleanly; the 5000 Hz upper limit leaves plenty of room. Suitable horns are in the 18Sound horns & waveguides category.
What to look out for
- 99 dB sensitivity with only 73 g of cone mass.
- 3.9 kg and 169 mm mounting depth: ideal for lightweight tops.
- 8 Ω, Re 5.6 Ω, 450 W AES on a 3" voice coil.
- Xmax 6.5 mm: bass-midrange driver, not a subwoofer.
- Vas 225 l: vented around 97 l, sealed mid chamber around 46 l as guide values.
Frequently asked questions
What sets the 15NMB420 apart from the 15MB700?
Both have Fs 42 Hz and Qts 0.29, but the 15MB700 uses a ferrite magnet and has Vas 202 l. The 15NMB420 is considerably lighter thanks to neodymium and has a slightly larger Vas of 225 l. If you want to save weight, go for the NMB420.
How high can I run the 15NMB420?
The stated range ends at 5000 Hz. In a 2-way top you sensibly cross well below that, so the compression driver takes over before the 15" cone beams too much.
Is the 15NMB420 enough as a bass without a subwoofer?
In a vented box around 97 l with f3 near 62 Hz it delivers solid kick bass. For extension below that you need a subwoofer, because 6.5 mm Xmax runs out quickly at low frequencies.
18Sound 15NMB420: manufacturer, spellings and classification
18Sound, 18 Sound and Eighteensound all refer to the same manufacturer: Eighteen Sound S.r.l. of Reggio Emilia, Italy. The 15NMB420 is a 15-inch woofer with neodymium magnet from the NMB series, available from 42.audio, 18Sound dealer in Germany, with datasheet and full specifications in the driver database.
At 42.audio you get the 18SOUND 15NMB420 with datasheet PDF, all key data in the driver database and the enclosure calculator. More drivers from this manufacturer: Atlas 18Sound.
Thiele-Small parameters
| Nominal impedance | 8 Ω |
|---|---|
| Resonance frequency fs | 42 Hz |
| Total Q Qts | 0.29 |
| Electrical Q Qes | 0.3 |
| Mechanical Q Qms | 6 |
| Equivalent volume Vas | 225.0 l |
| Moving mass Mms | 73.0 g |
| Cone area Sd | 900 cm² |
| Linear excursion Xmax | 6.5 mm |
| Force factor BL | 19 Tm |
| DC resistance Re | 5.6 Ω |
| Voice coil inductance Le | 0.8 mH |
Enclosure suggestion
The EBP of 140 suggests a bass-reflex enclosure. EBP = fs / Qes = 42 / 0.3
Sealed (Qtc 0.707)
- Enclosure volume Vb
- 45.5 l
- System resonance Fc
- 102 Hz
- Cut-off frequency F3
- 102 Hz
Bass reflex (QB3 after Small)recommended
- Enclosure volume Vb
- 75.7 l
- Tuning frequency Fb
- 59 Hz
- Cut-off frequency F3
- 68 Hz
Vb is the required net internal volume, Fb the tuning frequency of the reflex port and F3 the frequency at which the level has dropped by 3 dB. Calculated approximation after Small. A starting point for simulation, not a finished build plan.
Comparable drivers
Same size, same type, Qts within ±30 %.
- 18 Sound 15MB700fs 42 Hz · Qts 0.29 · Vas 202 l · in the shop
- Celestion TF1530fs 42 Hz · Qts 0.28 · Vas 162.2 l · in the database
- 18 Sound 15MB1000fs 48 Hz · Qts 0.31 · Vas 132.5 l · in the shop
- 18 Sound 15MB650fs 40 Hz · Qts 0.26 · Vas 210 l · in the shop
- 18 Sound 15NMB1000fs 46 Hz · Qts 0.24 · Vas 124 l · in the shop
- RCF MB15X301fs 38 Hz · Qts 0.34 · Vas 195 l · in the database
Specifications
| Allgemein | |
|---|---|
| Manufacturer | 18SOUND |
| Category | Low Frequency |
| Series | NMB |
| Magnet | Neo |
| Impedance (Ω) | 8 |
| Power handling (W) | 450 |
| Sensitivity (dB) | 99 |
| Frequency from (Hz) | 40 |
| Frequency to (Hz) | 5000 |
| Abmessungen & Korb | |
|---|---|
| Diameter | 15 |
| Voice coil (inch) | 3 |
| Mounting depth (mm) | 169 |
| Weight (kg) | 3.9 |
| Thiele-Small-Parameter | |
|---|---|
| Re (Ω) | 5.6 |
| Le (mH) | 0.8 |
| Fs (Hz) | 42 |
| Qms | 6 |
| Qes | 0.3 |
| Qts | 0.29 |
| Vas (l) | 225 |
| Xmax (mm) | 6.5 |
| BL (Tm) | 19 |
| Mms (kg) | 0.073 |
| Sd (m²) | 0.09 |